Manufacture of gilled tubes



April 23, 1935.

R. MAUTSCH MANUFACTURE OF GILLED TUBES Filed April 8, 1935 Patented Apr.23, 1935 1,998,552.

UNITED STATES PATENT OFFICE 1,998,552 MANUFACTURE OF GILLED TUBES RobertMautsch, Brussels, Belgium, assignor to Manufacture GeneraleMetallurgique, Societe Anonyme, Brussels, Belgium, a Belgian com-Application April 8, 1933, Serial No. 665,203 In Belgium April 12, 19323 Claims. (01. 113-118) This invention relates to the manufacture ofcreasing the surface available for heat exchange. gilled tubes of thetype used, more particularly, To expand the tubes, I may use anysuitable in heat exchange apparatuses. It is well-known means, ashydraulic pressure, or a mandrel either that the efliciency ofheat-exchange apparatuses rigid or expansible.-

5 comprising gilled tubes or pipes is largely de- My improved processinsures permanent and 5 pendent upon the closeness of the contactbeintimate contact between the tube and the gills, tween said tubes andthe gills mounted thereupon, the latter acting as powerful springs andbeing which may be secured in position by various permanently underelastic tension. It is parmeans, as by expanding said tubes, or bywelding, ticularly suitable for securing gills on thin for example. Ithas been proposed to improve walled tubes. I 10 the contact betweentubes and gills by combining Gilled tubes according to my invention anda the two said methods, or by providing the gills process for producingthe same are illustrated, with collars adapted to enclose a larger areaof by way of example, in the accompanying drawsaid tubes, or again bycorrugating or puckering ing whereof:

said gills. These various methods however can Fig. 1 is a diagrammaticview of a gilled tube 15 not be entirely relied upon to ensure strengthin provided with swellings according to the inventhe assembled unit, theability of the same to tion;

' withstand long use, or uniform contact between Fig. 2 shows said tubeat one stage of its progills and tubes at all points of the latterspeduction; I

riphery. Fig. 3 illustrates an alternative method for 20 The object ofmy invention is to provide tubes forming a e according to the invention;having gills firmly secured thereupon, in close Fig. 4 shows a tubeprovided with puckered contact therewith, by deforming the metal .ofgills.

= said tubes and making use of the resiliency of n t e Variou figures ofthe drawing, the tube the metal of said gills, under conditions calg n rlly designated y a is provi wi h a plu- 25 culated to ensuretherebetween a contact adapted a ity 0 gills designated by Con 0f highlyto remain permanent despite oxidation and other resilient metal, saidgills being mounted upon phenomena concomitant with the ageing of astubea which is thereupon subjected to internal sembled units. pressure as,for example, by having inserted In accordance with my invention I obtainthereinto a mandrel c whereof the diameter is 30 this result by makingthe gills of a metal the greater than the outer diameter of said tube.resiliency or the hardness of which has been Upon being moved in thedirection indicated by increased, by a mechanical or by a'thermictreatthe arrow (Fig. 2), the mandrel firstly expands ment for example,to such a degree that it is subthe tube at a. W n Passin through thePlane stantially greater than that of the-metal formof the first gill,the mandrel likewise expands 35 ing the tubes, and by causing theexpansion of said gill by elastic deformation. After the man,- the tubeto tension the metal of the gills sufdrel has passed beyond the gill(position shown ficiently to ensure that, on contracting after rein Fig.2) the considerable resilient energy stored lease of the pressureapplied for expanding the therein is released, and the gill contracts togrip 40 tube, each gill forms a constriction in the tube the tube, whilea swelling d is formed between 40 The metal forming the tubes may berendered said gill and the next in succession. Upon havingductile, forexample by an annealing treatment; been thus distorted, the gillpossesses suflicient in order to accentuate as much as possible thestored resilient energy to cause it to exert upon difference between theresiliency of the gills and the tube a degree of pressure which is allthe the lesser resiliency of the tubes- When the greater that theexpansion of the latter has been 45 metal of the tubes is relativelyvery ductile the more marked.

contraction of the gills may be suflicient to cause As shown in Fig. 1,the finished tube displays their inner edges to embed themselves in thetube a succession of swellings d, separated from each wall. other byconstrictions gripped by the gills.

In order that the gills be imparted a great Fig. 8 illustrates the useof an expansible manstiffness and shall not warp under the internal drele consisting, for example, of a resilient head pressure exerted by theexpanded tube, the gills and of a wedge-shaped member I, adapted to bemay advantageously be corrugated or puckered; m'oved intermittently andalternately, so that the' the corrugations formed in the gills thusproduce head member e may be expanded whenever situa new effect, inaddition to the known one of inated between two gills and thereby expandthe 55 It is generallyof advantage that the gills be formed of a highlyresilient metal, in order that the edges of their holes surrounding thetube should grip the latter firmly and exert permanent pressurethereupon. On the other hand, the metal of the tube must have a degreeof ductility sufhcient to cause swellings to be formed therein cientlystiff to remain unwarped by the expansion stresses set up'by the passageof the mandrel. To this end, the use of corrugated or, puckered finssuch as illustrated in Fig. 4 is of special advantage, the gill beingstifiened by numerous small folds or puckers formed therein, wherebystresses set up by the expansion of the tube are distributed uniformlythroughout said gill without causing the same to warp or distort beyondthe recuperative capacity of the metal of which it consists.

The process hereinbefore disclosed may of course be applied to tubeshaving a non circular cross-section or to an assemblage of finstraversed by several tubes, and the constructional embodiment of theinvention may be modified in various ways without departure from itsscope as'deflned in the appended claims.

I claim:

1. A process of manufacturing gilled tubes, comprising making gills of ametal substantially more resilient than. the metal of the tubes,threading the gills on a tube, passing through said tube a rigid mandrelof such size with re-' spect to the diameters of the tube and of theholes in the gills, that the tube is permanently deformed while thegills are only elastically deformed, thus causing the gills by theirsubsequent contraction to form constrictions in the tube and exert apredetermined elastic pressure thereon.

2. A process of. manufacturing gilled tubes, comprising forming gills ofsheet metal, hardening the metal of said gills, then threading saidhardened gills on a tube of relatively ductile metal, the holes in thegills being just large enough to accommodate said tube, passing throughsaid tube a rigid mandrel of such size with respect to the diameter ofthe tube that the tube is permanently expanded while the gills areelastically deformed, along the whole periphery of their holes, causingthe gills to contract, constrict the tube and exert thereon apredetermined elastic pressure.

3. The process of manufacturing gilled tubes comprising treating thegills to make the metal thereof substantially more resilient than themetal of the tube, then. placing a plurality of tract and formconstrictions in said tube.

ROBERT MAUTSCH.

